#define _CRT_SECURE_NO_WARNINGS 1

class Solution
{
public:
    int lengthOfLongestSubstring(string s)
    {
        int hash[128] = { 0 };
        int n = s.length();
        int ret = 0;
        for (int left = 0, right = 0; right < n; right++)
        {
            hash[s[right]]++;

            while (hash[s[right]] > 1)
                hash[s[left++]]--;

            ret = max(ret, right - left + 1);
        }
        return ret;
    }
};